Train Help--Venice to Salzburg

Try ÖBB or Trenitalia for Venice to Salzburg. Deutsche Bahn only sells tickets for trains involving Germany.

Meg,
On whether to book in advance for Italy or not, check the fares for your dates on the Trenitalia website (trenitalia.com). Between Rome, Florence and Venice you'll be on the Freccia (fast trains) or IC trains - and these trains do offer a significant savings if you book far enough in advance. There's a limited number of these fares, however, so they may be sold out by now. Pull up the website, search Rome to Florence for your travel date - see the possible times and see if there are discounted (economy or supereconomy) fares available for 4 people. If there are - consider booking, although this does lock you into that time (the tickets are non-refundable, non-exchangeable). If there aren't fares available or if you don't want to lock yourself into a certain time to travel between those cities in Italy, just buy your tickets when you are ready to leave.
Also note that when searching for tickets you'll find both Venezia Mestre and Venezia Santa Lucia, you want Venezia S. Lucia to actually be on the island. Similarly, there are multiple Florence stations - I imagine you will want Firenze Santa Maria Novella (SMN).

On Trenitalia's site, use the city spellings Devon posted.

Thanks for the suggestions. I'll probably look into booking Italy train tickets ASAP. As for Venice to Salzburg through Trenitalia's website, after entering my destinations, dates, etc., I keep getting a "This webpage has a redirect loop" message. Maybe it's just my computer? I've tried looking for these tickets on Trenitalia's website a few weeks ago, and I got this message then, too. The Man in Seat 61 suggests Venice to Verona or Innsbruck. Another option, maybe.

Meg,
I had trouble when I tried to do Venice to Salzburg on Trenitalia, too. My advice would be just to book it on the Austrian site (oebb.at). It went through when I tried that. You may get a message that part of your trip is not bookable on their website (for example, if it includes an Italian regional train from Venice to Verona). That's fine - you can just purchase that part of the ticket when you are in Italy. Regional trains don't sell out and there's no discount for purchasing in advance. If you want to see how much it will cost, just put enter that route in the Trenitalia site with a date within the next week - you'll see what the fare is.

How important is it to book train tickets between two countries ahead of time? For example, we'll be taking a train from Venice to Salzburg, Salzburg to Prague, a few more places already figured out, and then Freiburg to Paris. We only have about a month before all of these trips, so is it still worth it to try to book in advance? I'm worried because there are 4 of us, and I want to make sure we are all on the same train. Our lodging is all taken care of, so we do have a deadline to get to the places where we're staying (though, if something happened, missing a night wouldn't be the worst thing in the world).

We're trying to find the cheapest option available at this point, but we're also worried about booking in advance and something going wrong, such as missing a train or something. Is it worth the risk?

The cheapest option is always to buy in advance to get the best price. It is already a bit late for your Italian legs, but you may find something. Besides price, buying in advance with seat reservations guarantees you all can sit together. It is unlikely, even unheard of, that you would have to travel on separate trains, but someone may have to stand part of the way. Trains within Czech Republic probably will not have advance purchase discounts, they are already plenty cheap.
Plus you will know what your spending on transportation ahead of time. You wouldn't just show up at the airport and say "Get me on the next flight to Rome." You'd be at the mercy of whatever number they threw at you.
Another advantage is if you already have a ticket, you just get on the train before it departs, even it is by one second. (Don't try the running down the platform and jumping on a moving train. That only works in Hollywood.) If you show up and there is a huge line at the ticket window, and you can't figure out how the vending machines work, or your credit card doesn't work in them, you'll still miss the train.

Thanks, Sam; that helps a lot!